Differential and method of assembly thereof

ABSTRACT

A differential including axle pinions and pinion gears and a body having two parts between which the pinions are mounted. The two parts of the body are provided with complementary guiding surfaces for guiding the two parts in adjustment relative to one another along an input and output axis. One of the two parts includes at least two inner guides for slidably and adjustably mounting a rotatable assembly pin of the pinion gears such that when a relative position of the two parts is adjusted, an axial play of at least the axle pinions or a differential drag torque is adjusted afterwhich the two parts are locked relative to each other.

BACKGROUND OF THE INVENTION

The present invention relates to differentials of which the body, insidewhich are mounted the axle pinions and the pinion gears, is in twoparts. More precisely, it relates to this body, to a differentialcomprising this body, as well as to a method for assembling thisdifferential.

DESCRIPTION OF THE RELATED ART

A known differential comprises two substantially symmetricalhalf-shells. The latter, once assembled by clamping one against theother, form the body of the differential and jointly define a housingcontaining in particular two axle pinions, two pinion gears and twopierced dish elements, each disposed between one of the axle pinions andthe body of the differential. Due to the manufacturing tolerance of theparts constituting this differential, an adjustment of the play betweenits gears is provided during assembly thereof. To that end, a pluralityof dish elements of different thicknesses are successively mounted untilthose which enable the desired adjustment to be obtained have beenfound. Apart from being tedious, this manner of proceeding is long andmust be carried out manually.

Patent document JP-58 211053 describes a differential, in a cage ofwhich are screwed a first and a second tubular element. The adjustmentof the play inside this differential requires adjusting both theposition of the first tubular element and that of the second tubularelement.

SUMMARY OF THE INVENTION

The invention therefore has for its object to facilitate the adjustmentof a play inside a differential and/or the drag torque of thisdifferential.

Within its meaning to be understood here, the drag torque of adifferential is the torque which must be exerted on one of its axlepinions to drive this axle pinion when, the other axle pinion being freeto rotate, the body of the differential is immobilized. As will havebeen understood, the drag torque depends in particular on the playsinside the differential.

For the purpose of attaining the object set forth hereinabove, theinvention relates to a differential body inside which are intended to bemounted two axle pinions and at least two pinion gears, each in meshwith the two axle pinions, this body comprising first and second partsintended to be assembled, these first and second parts comprisingcomplementary guiding means adapted to guide them in relative approachand removal along the axis of rotation of the differential,characterized in that the first part comprises at least two inner guidesfor slidably mounting at least one pin for rotatable assembly of atleast one of the pinion gears, each of these two guides joining twopoints offset from each other in a direction parallel to the axis ofrotation of the differential.

The invention also has for its object a differential comprising at leasttwo axle pinions, two pinion gears, each in mesh with the two axlepinions, and a body inside which are mounted the axle pinions and thepinion gears. The body including assembled first and second parts and atleast one pin for rotatable assembly of the pinion gears being mountedto slide relative to the first part. The relative position of the firstand second parts being adjusted so that the axle pinions have apredetermined axial play or so that the differential has a predetermineddrag torque. The first and second parts being locked in this adjustedrelative position.

Moreover, the invention has for an object a method for assembling thedifferential as defined hereinabove, characterized in that it comprisesat least the steps in which:

a) at least the axle pinions and the pinion gears are disposed betweenthe first and second parts;

b) the relative position of said first and second parts is adjusted soas to adjust the axial play of at least one of the axle pinions or thedrag torque of the differential, and

c) the first and second parts are locked in the position determinedduring step b.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood on reading the followingdescription, given solely by way of example and made with reference tothe accompanying drawings, in which:

FIG. 1 is a view in axial section of a differential according to theinvention.

FIG. 2 is an exploded view, in perspective, and represents the body, intwo parts one and the other according to the invention, of thedifferential of FIG. 1, one of these two parts being provided with twodish elements constituent of the differential.

FIG. 3 is a view in axial section of one of these two constituent dishelements of the differential shown in FIG. 1, and

FIG. 4 shows the dish element of FIG. 3, this dish element being viewedby that of its two opposite faces which is intended to be turnedoutwardly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a differential which is according to the invention andcomprises a body 1 in two parts, namely a cage 2 and an obturator 3. Inthis body 1, which defines an inner housing 4, there are mounted twoaxle pinions 5, two pinion gears 6, two anti-friction dish elements 7disposed opposite each other, two sliding dish elements 8 likewisedisposed opposite each other and an assembly pin 9 which is engaged inthe sliding dish elements 8 and bears the pinion gears 6.

As may also be seen in FIG. 2, the cage 2 is substantially in the formof a solid of revolution which has axis A of rotation of thedifferential as axis of revolution. It essentially defines the innerhousing 4 and comprises an opening 10 for access to this housing 4. Thisopening 10 is defined by an end portion 11 of the inner surface of thecage 2. This end portion 11, which has a circular section, is machinedand forms guiding means. It comprises two adjacent portions of which oneis disposed more deeply than the other and referenced 12, and of whichthe other is referenced 13. Portion 12 is tapped, while portion 13 isbored.

Beyond the inner housing 4, the cage 2 extends in a tubular portion 14which is disposed and directed opposite the access opening 10, and whichis provided for the passage of a transmission shaft (not shown) intendedto be coupled to one of the axle pinions 5.

Between the end portion 11 and the tubular portion 14, the inner surfaceof the cage 2 includes substantially cylindrical portion 15 adjacent theend portion 11, then it terminates in a bottom surface 16, which, forits part, is concave and substantially spherical. In the portion 15, twoinner grooves 17 are provided, disposed opposite and substantiallyaxial. Each of these grooves 17, of which the respective bottoms andsides are planar, forms a guide in which is slidably mounted one of thetwo dish elements 8. The grooves extend between two points “B” and “C”that are offset with each other in a direction that is parallel to theAxis “A” of rotation or the input and output axis of the differential.

In the vicinity of its access opening 10, the cage 2 comprises an outer,radial ring 18 which forms a flange for fixing by clamping a crown wheel(not shown) provided for drive of the differential. The radial ring 18is pierced with holes 19 for the passage of screws (likewise not shown),for fixing the crown wheel.

The cage 2 is a forged part in one piece. It is preferably made of alight alloy such as an aluminium alloy. Except for the end portion 11,its inner surface is not machined, this compensating, at least in part,the additional costs involved by the use of forging, compared to amethod of molding.

The obturator 3 is likewise substantially in the form of a solid ofrevolution of which the axis is the axis A of rotation of thedifferential. It comprises a tubular part 20 which is provided for thepassage of another transmission shaft (not shown) intended to be coupledto one of the axle pinions 5. This tubular part 20 widens then extendsin a thick, radial, annular cover 21.

The lateral edge of this cover 21 is defined by a cylindrical surface22, which forms complementary guiding means of the end portion 11. Likethe latter, the cylindrical surface 22 is machined and comprises asmooth portion 23 and a threaded portion 24.

The inner wall 25 of the lid 21 partly defines the inner housing 4. Inits central part, it is also concave and substantially spherical.

The two sliding dish elements 8 are identical, this being translated, onthe one hand, by a simplification of the assembly of the differentialand, on the other hand, by a saving. One of them is shown in FIGS. 3 and4 and is substantially annular in shape. It comprises a substantiallytubular base 26, of which the inner section is circular and whose outersection is likewise circular except at the level of two rectilinearshoulders 27, parallel to each other and arranged opposite each other.The lateral faces 28 of these two shoulders 27 are intended to cooperatewith the sides of the grooves 17, in order to ensure, on the one hand,guiding of the corresponding dish element 8, particularly duringassembly thereof and, on the other hand, the transmission of the effortsbetween the cage 2 and the assembly pin 9.

The inner surface of the base 26 defines a housing for one of the endsof the assembly pin 9. In the example shown, this housing has a circularcross section so that it behaves like a bearing.

From the base 26 there widens a seat 29 for one of the pinion gears 6.The inner surface of this seat 29 is a surface of revolution which isconcave and substantially spherical, and it is separated from the innersurface of the base 26 by an annular flange 30, directed along the axisof the dish element 8 and provided for centering one of the pinion gears6.

Each dish element 8 is a part in one piece, cold-forged and made of ametal.

Each of the gears 5 and 6 is known per se and presents a conicaltoothing and a convex and substantially spherical outer face.

Each dish element 7 presents the shape of a plate of small thickness,pierced with a central hole for the passage of a transmission shaft andconvex in the manner of a substantially spherical dome.

The assembly pin 9 is formed by a cylindrical bar of circular section.

In order to assemble the differential shown in FIG. 1, a dish element 7,then an axle pinion 5, are firstly introduced inside the cage 2.

Then, after having fitted the two pinion gears 6 and the two dishelements 8 on the assembly pin 9, the assembly thus formed is engaged inthe housing 4, taking care to place the bases 26 of the elements 8 inthe grooves 17. This assembly is then pushed towards the bottom of thecage 2, by simultaneously sliding one and the other dish elements 8 inthe guides formed by the grooves 17. It will be noted to what point thepinion gears 6, the assembly pin 9 and the two dish elements 8 areeasily and rapidly mounted, insofar as they are all positioned at thesame time. The step being described is terminated once the other axlepinion 5 and the other dish element 7 have also been disposed inside thecage 2, and the obturator 3 has been pre-positioned at the level of theaccess opening 10.

The step of adjusting the drag torque of the differential or of theplay, along axis A, of the mechanism inside the body 1 then begins. Thisadjustment is effected by screwing the cover 21 more or less deeply inthe cage 2, which may be effected by an automat acting from a continuousmeasurement or from successive measurements of the drag torque. In avariant, it is possible to proceed in the following manner: one beginsby screwing the obturator 3 in the cage 2 completely, i.e. until theycome into abutment, then this obturator 3 is unscrewed by a quantitycorresponding to the desired play. It will be noted that the threadedportions 12 and 24 in cooperation form means for adjusting withprecision the relative position, in approach-removal along axis A, ofthe cage 2 and of the obturator 3. As the assembly pin 9 is mounted toslide along axis A, with the aid of the dish elements 8, it ispositioned by itself inside the cage 2, with the result that the axialplays of the two axle pinions 5 are adjusted simultaneously in oneoperation.

Once the relative position of the cage 2 and of the obturator 3 isadjusted, these latter are immobilized with respect to each other withthe aid of locking means which, in the example shown, are formed by awelding bead 31 arranged along the edge of the cover 21, as well as by apin 32 inserted by force in a hole pierced both in the cage 2 and theobturator 3, where the end portion 11 and the cylindrical surface 22cooperate.

The adjustment and assembly which have just been described areparticularly simple and rapid to carry out, in accordance with theobject that the invention intends to attain.

Moreover, contrary to the prior art mentioned in the introduction, it isnot necessary to manufacture, manage and store a whole set of dishelements of different thicknesses.

In addition, the adjustment of the play or of the drag torque may beautomated.

FIG. 1 shows the differential as arranged when all the steps forassembly described previously have been carried out. The cage 2 and theobturator 3 are in that case rigidly associated coaxially. They retaintherebetween, with reduced play in the direction defined by axis A, thewhole mechanism and in particular the axle pinions 5. The pin 9, onwhich the pinion gears 6 are idly mounted, is therefore common to thelatter, this simplifying the assembly of the differential and giving thewhole an increased rigidity. The shape of the seats 29 of the dishelements 8 is such that it promotes the rotation of the pinion gears 6,just like the anti-friction dish elements 7 promote the rotation of theaxle pinions 5. These anti-friction dish elements 7 are all the moreuseful as the surfaces of the body 1 on which they are applied are notmachined.

The invention is not limited to the form of embodiment describedhereinbefore.

In particular, one of the two locking means constituted by the weldingbead 31 and the pin 32 may be eliminated, while retaining the other.Moreover, these locking means may be replaced or completed by others,such as for example a threaded ring, clamped against the cover 21 byscrewing in the cage 2, in the manner of a counter-nut. The desiredlocking may also be obtained by crimping the cage 2 on the obturator 3or by adhesion.

Moreover, although the differential described hereinbefore by way ofexample comprises only two pinion gears 6, a differential which presentsmore of them, for example three or four, does not depart from the scopeof the invention.

With respect to the known differentials in which no adjustment of thedrag torque is effected, a differential according to the inventionpresents improved operational performances.

1. A differential body comprising first and second parts inside whichare mounted two axle pinions that are in mesh with at least two piniongears, each of the first and second parts including complementaryportions that are adapted to guide them as they are moved toward or awayfrom one another along an input and output axis (A) of the differential,said first part including at least two inner guides, a pin on which thepinion gears are mounted, each of the two inner guides extending betweentwo points B and C that are offset from each other in a directionparallel to the input and output axis (A) of the differential, the pinbeing freely slidable along the two inner guides as the first and secondparts of the differential body are assembled, the first and second partsfurther including means for adjusting a relative position of the firstand second parts relative to one another in assembled relationship, andthe means for adjusting including a threading and a tapping which arecomplementary to one another and which are provided on at least aportion of the complementary guide portions of the first and secondparts.
 2. The differential body of claim 1, wherein the first part has ashape of a cage defining a housing for the axle pinions and piniongears, the cage including an opening for access into the housing, theopening being obturated by the second part.
 3. The differential body ofclaim 2, wherein the first part is a forged piece having inner surfaceswhich defined the housing which are free of machining marks.
 4. A methodfor assembling a differential comprising at least two axial pinions, twopinion gears in mesh with the two axle pinions, a body having first andsecond parts defining a housing inside which are mounted the axlepinions and the pinion gears, each of the first and second partsincluding complementary portions that are adapted to guide them as theyare moved toward or away from one another along an input and output axis(A) of the differential, a pin on which the pinion gears are mounted,means for mounting the pin to slide within the housing, the first andsecond parts further including means for adjusting a relative positionof the first and second parts relative to one another in assembledrelationship so that the axle pinions have a predetermined axial play orso that the differential has a predetermined drag torque and the meansfor adjusting including a threading and a tapping which arecomplementary to one another and which are provided on at least aportion of the complementary guide portions of the first and secondparts, and means for locking the first and second parts in an adjustedposition, the method including at least the steps of: a) placing the atleast two axle pinions and the pinion gears mounted on the pin betweenthe first and second parts; b) adjusting the relative position of thefirst and second parts by relative rotation of the means for adjustingso as to adjust an axial play of at least one of the axle pinions or thedrag torque of the differential, and c) locking the first and secondparts in the position determined during step b).
 5. The method forassembly according to claim 4, wherein as part of step a), slidablymounting the pin inside the first part.
 6. A differential comprising atleast two axle pinions, two pinion gears in mesh with the two axlepinions, a body having first and second parts defining a housing insidewhich are mounted the axle pinions and the pinion gears, each of saidfirst and second parts including complementary portions that are adaptedto guide them as they are moved toward or away from one another along aninput and output axis (A) of the differential, said first part includingat least two inner guides, a pin on which the pinion gears are mounted,each of the two inner guides extending between two points B and C thatare offset from each other in a direction parallel to the input andoutput axis (A) of the differential, the pin being freely slidable alongthe two inner guides as the first and second parts of the differentialbody are assembled, the first and second parts further including meansfor adjusting a relative position of the first and second parts relativeto one another in assembled relationship, the means for adjustingincluding a threading and a tapping which are complementary to oneanother and which are provided on at least a portion of thecomplementary guide portions of the first and second parts, the relativeposition of the first and second parts being adjustable as they arebeing assembled so that the axle pinions have a predetermined axial playor so that the differential has a predetermined drag torque, and meansfor locking the first and second parts in the adjusted position.
 7. Adifferential according to claim 6, including two dish parts eachdefining a housing receiving an end of the pin, each of the two innerguides being in a shape of a groove in which one of the two dish partsslides.
 8. A differential according to claim 6, wherein the means forlocking the first and second parts in the adjusted position includes apin element.
 9. A differential according to claim 6, wherein each of thefirst and second parts includes an inner surface, said inner surfacesbeing arranged opposite one another and being substantially concave, andtwo anti-friction dish elements, each placed between one of the twosubstantially concave surfaces and a substantially convex surface of oneof the axle pinions.
 10. A Differential comprising at least two axlepinions which are in mesh with at least two pinion gears, a body inwhich the axle pinions and the pinion gears are mounted, the bodyincluding first and second parts betweem which the axle pinions and thepinion gears are mounted, each of the first and second parts includingcomplementary portions that are adapted to guide them as they are movedtoward or away from one another along an input and output axis (A) ofthe differential, said first part including at least two inner guides, apin on which the pinion gears are mounted, each of the two inner guidesextending between two points B and C that are offset from each other ina direction parallel to the input and output axis (A) of thedifferential, the pin being freely slidable along the two inner guidesas the first and second parts of the differential body are assembled,the first and second parts further including means for adjusting arelative position of the first and second parts relative to one anotherin assembled relationship, and the means for adjusting including athreading and a tapping which are complementary to one another and whichare provided on at least a portion of the complementary guide portionsof the first and second parts.